Question

Sugar which does not give reddish brown precipitate with Fehling‟s reagent is:

• A. Lactose
• B. Maltose
• C. Sucrose
• D. Glucose

Answer 1

Answer: (C)

Sucrose

Answer 2

Step 1. Identify the Requirement for Fehling’s Test: Fehling’s reagent specifically reacts with reducing sugars that contain a free aldehyde or ketone group.
Step 2. Evaluate the Sugars: Sucrose: It is a non-reducing sugar because it lacks a free hemiacetal group due to its glycosidic linkage between glucose and fructose units. Lactose, Glucose, and Maltose: These are reducing sugars with free hemiacetal groups, allowing them to react with Fehling’s reagent and produce a reddish-brown precipitate.
Step 3. Conclusion: Since sucrose does not have a free aldehyde or ketone group, it does not give a positive test with Fehling’s solution.